Multicolored and white-light phosphors based on doped GdF3 nanoparticles and their potential bio-applications.
ABSTRACT Rare-earth-doped gadolinium fluoride nanocrystals were synthesized by a single step synthesis employing ethylene glycol as solvent. Based on X-ray diffraction studies, stabilization of hexagonal modification of GdF(3) has been inferred. The microscopic studies show formation of uniformly distributed nanocrystals (~15 nm). The nanoparticles are readily dispersible in water and show bright luminescence in colloidal solution. The luminescence properties have been investigated as a function of activator concentrations, and enhanced optical properties have been attributed to efficient energy transfer from the Gd(3+) to the activator RE(3+) ions, which has further been confirmed by steady-state and time-resolved optical studies. It has been demonstrated that on doping appropriate amount of activators in host GdF(3), a novel white-light-emitting phosphor is obtained with CIE co-ordinates and correlated color temperature (CCT) very close to broad daylight. This can have promising applications as phosphor for white-light ultraviolet-light-emitting diodes (UV-LEDs). Our experiments showed efficient labeling of human breast carcinoma cells (MCF-7) by Tb(3+)-doped GdF(3) nanoparticles. The fluorescence intensity was found to be dependent on the surface modifying/coating agent, and the results were validated using confocal microscopy in terms of localization of these functionalized nanoparticles.
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ABSTRACT: BACKGROUND and The association between hyperthermia and early neurological deterioration, increased morbidity, and mortality in acute ischemic stroke is well known. However, the timing at which the cerebral lesion may be aggravated by high temperature has not been firmly established. The aim of this study was to determine the prognostic value of body temperature measured at different times after onset of stroke. Axillary temperature was recorded every 2 hour hours for 72 hours in 260 patients with a hemispheric cerebral infarction of <24 hours' duration. A potential infectious focus was examined in all patients with hyperthermia (temperature >37.5 degreesC in any of the assessments). Stroke severity was quantified with the Canadian Stroke Scale on admission. The relationship between the highest temperature recorded in each 6-hour interval from stroke onset and stroke outcome (Canadian Stroke Scale and Barthel Index at 3 months) or infarct volume was evaluated by correlation analyses. The importance of the time at which hyperthermia was first detected was assessed by logistic regression analysis. During the first 72 hours, 158 patients (60.8%) had hyperthermia, and in 57.6% of them an infectious cause was identified. Mortality rate at 3 months was 1% in normothermic patients and 15.8% in hyperthermic patients (P<0.001). The correlation coefficients between the final infarct volume, Canadian Stroke Scale and Barthel Index scores at 3 months, and each temperature recording decreased progressively over time from symptom onset. Hyperthermia initiated within the first 24 hours from stroke onset, but not afterward, was independently related to larger infarct volume (odds ratio [OR]=3.23, 95% CI=1.63 to 6.43; P<0.001) and higher neurological deficit (OR=3.06, 95% CI=1.70 to 5.53; P<0. 001) and dependency (OR=3.41, 95% CI=1.69 to 6.88; P=0.002) at 3 months. The infectious origin of hyperthermia was not associated with poorer outcome or greater infarct volume. The relationship between brain damage and high temperature is greater the earlier the increase in temperature occurs. However, only body temperature within the first 24 hours from stroke onset is associated with poor outcome and large cerebral infarcts.Stroke 01/1999; 29(12):2455-60. · 6.16 Impact Factor
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ABSTRACT: Exposure to maternal or placental infection is related to risk of preterm birth and, in premature infants, of brain lesions predictive of cerebral palsy (CP). Few studies have investigated whether maternal infection is associated with risk of CP in children of normal birth weight. To investigate maternal infection during the admission for delivery as a possible risk factor for CP in infants born weighing 2500 g or more. Population-based case-control study. All hospitals in 4 northern California counties, 1983 through 1985. A total of 46 children with disabling spastic CP who had no recognized prenatal brain lesions and 378 randomly selected control children weighing 2500 g or more at birth and surviving to age 3 years. Disabling spastic CP and signs of neonatal morbidity. Maternal fever exceeding 38 degrees C in labor was associated with increased risk of unexplained CP (odds ratio [OR], 9.3; 95% confidence interval [CI], 2.7-31.0), as was a clinical diagnosis of chorioamnionitis. One or more indicators of maternal infection were present in 2.9% of control children, 22% of children with CP (OR, 9.3; 95% CI, 3.7-23.0), and 37% of those with the spastic quadriplegic subtype of CP (OR, 19.0; 95% CI, 6.5-56.0). Newborns exposed to maternal infection, both cases and controls, had 5-minute Apgar scores below 6 more often than those unexposed. Among children with CP, those born to infected women were more often hypotensive, needed intubation, had neonatal seizures, and received a clinical diagnosis of hypoxic-ischemic encephalopathy. Intrauterine exposure to maternal infection was associated with a marked increase in risk of CP in infants of normal birth weight. Maternal infection was also linked with low Apgar scores, other evidence of hypotension [corrected] and need for resuscitation, and neonatal seizures-signs commonly attributed to birth asphyxia.JAMA The Journal of the American Medical Association 08/1997; 278(3):207-11. · 29.98 Impact Factor
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ABSTRACT: To investigate the relation between lesion volume, lesion location, and clinical outcome in children with infarction in the territory of the middle cerebral artery (MCA). Children with MCA territory infarcts were selected retrospectively from a database of children with ischaemic stroke. Lesion volumes were expressed as a percentage of the supratentorial intracranial volume and were categorised as "small", "moderate", or "large". Lesion location was categorised as cortical or purely subcortical. Outcome was ascertained by parental questionnaire and was categorised as "good" or "poor". 38 patients were identified (median age 6 years); 21 patients had lesions that involved cortical tissue. Outcome was good in 12 cases and poor in 26 cases (including 2 children who died). Although there was no significant effect of lesion size or lesion location on outcome for the group as a whole, all children who had infarcted more than 10% of intracranial volume had a poor outcome. Of note, some children with small subcortical lesions had pronounced residual deficits. Although the outcome after a small infarct in the MCA territory is variable and unpredictable, infarction of more than 10% of intracranial volume is universally associated with a poor outcome. Characterisation of lesion volume and topography might be helpful in identification of such children for participation in future trials of treatments for acute stroke.Archives of Disease in Childhood 11/1999; 81(4):295-300. · 3.05 Impact Factor